Rational Design of an Efficient S-Scheme Heterojunction of CdS/Bi2WO6-S Nanocomposites for Photocatalytic CO2 Reduction

CdS/Bi2WO6-S nanocomposites, in which small cubic CdS nanoparticles (ca. 4 nm) assembled on thin orthorhombic Bi2WO6 nanosheets (Bi2WO6-S), were fabricated through a facile precipitation of Cd2+ with S2- in the presence of orthorhombic Bi2WO6 nanosheets obtained via a colloidal two-phase method. As a result of the presence of an efficient S-scheme charge transfer pathway between CdS and Bi2WO6S, the as-obtained CdS/Bi2WO6-S nanocomposites exhibit superior activity for photocatalytic CO2 reduction to generated CO and CH4 under visible light, with an optimum performance observed over the 0.5 CdS/Bi2WO6-S nanocomposite. The obvious superior activity over the 0.5 CdS/Bi2WO6-S nanocomposite compared to that over the 0.5 CdS/Bi2WO6-B nanocomposite, in which cubic CdS nanoparticles were deposited on bulk Bi2WO6, highlights the importance of a rational interface engineering in the fabrication of the S-scheme heterojunction photocatalytic systems. This work demonstrates that both a rational selection of two photocatalysts with staggered band alignment and a delicate tuning of their interface are important in the fabrication of the S-scheme heterojunction to realize an efficient photocatalysis.